The present invention relates to rotary regenerative heat exchangers and more particularly to the vertical housing panels and the connection between these panels and the horizontal flange plate on connecting duct assemblies.
A rotary regenerative heat exchanger, conventionally used as an air preheater for combustion equipment, is composed of a rotor containing heat exchange surface which is mounted on a vertical shaft for rotation within a heat exchanger housing which surrounds the rotor. Extending across the lower end of the heat exchanger, normally the cold end, below the housing is a cold end center section which serves as a support for the entire heat exchanger structure including the rotor. Extending across the top of the heat exchanger above the housing and parallel to the cold end center section is a hot end center section. This hot end center section functions as the mounting means for the upper end of the rotor shaft. The hot end center section is supported by main support pedestals on each end of the hot end center section which are, in turn, supported on the ends of the cold end center section.
The housing comprises a plurality of vertical housing panels arranged around the periphery of the rotor. Typically, there are eight or more such panels that form the housing. Attached to each end of the heat exchanger are the connecting plate duct assemblies. There are connections which make the transition between the duct work, which is usually rectangular, and the generally circular heat exchanger and they are attached to the sides of the hot and cold end center sections. The vertical housing panels are attached to and between these connecting plate duct assemblies thereby forming the housing around the rotor and forming the flow path for the air and gas through the rotor. In the normal arrangement, circumferential bypass seals are provided between the rotor and the housing, or the connecting plate duct assemblies to which the housing is attached, to prevent the air and gas from flowing around the outside of the rotor.
In prior art rotary regenerative heat exchangers, the vertical housing panels are formed with flanges on each end. The flange on the bottom of each panel is bolted to a mating horizontal flange plate attached to the cold end connecting plate duct assemblies. Likewise, the flange on the top of each panel is bolted to a mating horizontal flange plate on the hot end connecting plate duct assemblies. In order to assure the fit of the vertical housing panels between the mating flanges on the connecting plate duct assemblies, the vertical housing panels must be manufactured to length within rather close tolerances. This tolerance normally provides for a small designed-in gap between the top flange of the vertical housing panels and the mating flange on the connecting plate duct assemblies. During the field assembly, the alignment holes for the bolts that fasten the vertical housing panels to the horizontal flanges on the connecting plate duct assemblies are hand drilled. After field assembly when these flanges are bolted together, a round rod is welded or otherwise attached around the outside of the gap to form a seal.